Haddock are native to the North Atlantic and occur on both sides of the ocean. In the northwest Atlantic they range from the Strait of Belle Isle to New England, while in the northeast they are found in the Bay of Biscay northwards around Scandinavia into the Russian Arctic. In Canada, the most important populations occur from the Bay of Fundy to Cape Breton and the Grand Banks. A deep-sea fish, haddock usually live at depths of 50-250 m.

Haddock are an elongated fish with a forked tail, dark purplish-grey on their head and back and a black lateral line. They have three dorsal fins, the first triangular and the next two squarish. Their coloration gets lighter below their lateral line, becoming silvery grey with a pink tinge and white on their belly and under their head. They have a large, distinctive black spot over their pectoral fins. Their maximum length is about 100 cm and maximum weight around 4 kg.